JP2016003707A - Work vehicle - Google Patents

Work vehicle Download PDF

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Publication number
JP2016003707A
JP2016003707A JP2014124080A JP2014124080A JP2016003707A JP 2016003707 A JP2016003707 A JP 2016003707A JP 2014124080 A JP2014124080 A JP 2014124080A JP 2014124080 A JP2014124080 A JP 2014124080A JP 2016003707 A JP2016003707 A JP 2016003707A
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Japan
Prior art keywords
vehicle speed
control unit
depression amount
engine
depression
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JP2014124080A
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Japanese (ja)
Inventor
康平 小倉
Kohei Ogura
康平 小倉
晃史 黒田
Akishi Kuroda
晃史 黒田
Original Assignee
ヤンマー株式会社
Yanmar Co Ltd
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Application filed by ヤンマー株式会社, Yanmar Co Ltd filed Critical ヤンマー株式会社
Priority to JP2014124080A priority Critical patent/JP2016003707A/en
Publication of JP2016003707A publication Critical patent/JP2016003707A/en
Pending legal-status Critical Current

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Abstract

In a work vehicle having a continuously variable transmission, an operator can finely adjust a vehicle speed by using a foot. A tractor includes an engine, a hydraulic HMT, front and rear wheels, a potentiometer, and a transmission control unit. The hydraulic HMT shifts the output of the engine. The front and rear wheels use the output of the HMT to drive the vehicle body. The potentiometer detects the depression amount of the clutch pedal. The transmission control unit calculates a target vehicle speed based on the depression amount detected by the potentiometer, and performs control to change the vehicle speed based on the target vehicle speed. [Selection] Figure 6

Description

  The present invention relates to a work vehicle that travels by changing the output of an engine with a continuously variable transmission.

  2. Description of the Related Art Conventionally, in a work vehicle such as a tractor, a configuration including a hydraulic continuously variable transmission is known in order to smoothly run in a farm field. Patent Document 1 discloses this type of continuously variable transmission, and Patent Document 2 discloses a work vehicle equipped with a continuously variable transmission.

  The continuously variable transmission of Patent Document 1 is an HMT (hydraulic-mechanical transmission) including an HST (hydrostatic continuously variable transmission) and a planetary gear type differential. This continuously variable transmission has a mode in which the engine output is shifted by the HST and a mode in which the engine output is shifted by the HST and the planetary gear. These modes are switched by a clutch provided in the HMT. When the clutch pedal of the work vehicle is depressed, the clutch is controlled so that the engine output is not transmitted to the wheels.

  The work vehicle of patent document 2 detects the depression amount (operation position) of a brake pedal. In this work vehicle, the continuously variable transmission is changed to the low speed side as the amount of depression of the brake pedal increases.

Japanese Patent No. 4439183 Japanese Patent No. 50275596

  By the way, when an operator attaches a work machine (attachment) to the rear of the work vehicle, it is necessary to perform alignment by retreating the work vehicle while looking at the work machine behind. At this time, since the operator reverses the body and confirms the rear, it is difficult to finely adjust the vehicle speed using the shift lever. Further, when the work vehicle performs work while traveling near the heel, it is necessary to confirm the positional relationship with the heel while operating the work machine, so that it is difficult to finely adjust the vehicle speed using the shift lever.

  Here, a tractor including a mechanical transmission can finely adjust the vehicle speed by adjusting the amount of depression of the clutch pedal (so-called half-clutch). On the other hand, as in Patent Documents 1 and 2, in the case of a tractor including a hydraulic continuously variable transmission, a half-clutch cannot be performed, and thus the operator cannot finely adjust the vehicle speed using his / her feet.

  The present invention has been made in view of the above circumstances, and a main object thereof is to provide a configuration in which an operator can finely adjust a vehicle speed by using a foot in a work vehicle including a continuously variable transmission. There is.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, a work vehicle having the following configuration is provided. That is, this work vehicle includes an engine, a continuously variable transmission, a traveling unit, a stepping amount detection unit, and a control unit. The continuously variable transmission is hydraulic and shifts the output of the engine. The travel unit travels the vehicle body by the output of the continuously variable transmission. The depression amount detection unit detects the depression amount of the clutch pedal or the brake pedal. The control unit calculates a target vehicle speed that decreases as the stepping amount increases based on the stepping amount detected by the stepping amount detection unit, and performs control to change the vehicle speed based on the target vehicle speed.

  Thus, since the clutch pedal or the brake pedal can be operated with the foot, the speed of the work vehicle can be adjusted even in a situation where it is difficult to operate the shift lever. Therefore, the speed of the work vehicle can be finely adjusted with a simple operation even when the work machine is attached or detached or when the work is on the near side.

  The work vehicle preferably has the following configuration. That is, the depression amount detection unit detects the depression amount of the clutch pedal or the brake pedal. The control unit cuts off the power transmitted from the engine to the traveling unit when the stepping amount becomes a predetermined threshold value or more.

  As a result, the operator can finely adjust the vehicle speed using the clutch pedal or the brake pedal with the same operation feeling as that of the half clutch.

  The work vehicle preferably has the following configuration. That is, a vehicle speed corresponding to the depression amount is set in advance. The control unit controls the vehicle speed corresponding to the depression amount detected by the depression amount detection unit as the target vehicle speed.

  As a result, the vehicle speed is determined only in accordance with the depression amount, so that the operator can easily realize the desired vehicle speed by grasping the correspondence between the depression amount and the vehicle speed.

  The work vehicle includes a vehicle speed operation unit capable of instructing a vehicle speed. The control unit determines a vehicle speed based on at least one of an instruction content of the vehicle speed operation unit and an engine rotation speed in addition to the depression amount detected by the depression amount detection unit, and determines the determined vehicle speed as the target Control as vehicle speed.

  As a result, the work vehicle can be driven at a highly appropriate vehicle speed in consideration of the operator's instruction, the state of the engine, and the like.

The side view of the tractor concerning a 1st embodiment of the present invention. The skeleton figure which shows the power transmission path | route of a tractor. The top view which shows the operation tool provided in the cabin. The block diagram which shows the structure which controls HMT. The flowchart which shows the vehicle speed adjustment control which a transmission control part performs. The graph which shows the relationship between the depression amount of a clutch pedal, and a pedal adjustment vehicle speed. The figure which shows a mode that a vehicle speed changes according to the depression amount of a clutch pedal. The skeleton figure which shows the power transmission path | route of the tractor which concerns on 2nd Embodiment.

  Next, an embodiment of the invention will be described with reference to the drawings. FIG. 1 is a side view of a tractor 10 as a work vehicle according to a first embodiment of the present invention.

  The tractor 10 is a work vehicle for agricultural work, and can be equipped with various work machines (attachments) such as a rotary, a loader, a plow, a box scraper, and the like to perform various work using the work machine. it can. In the following description, “left side”, “right side”, and the like simply mean the left side and the right side in the direction in which the tractor 10 moves forward.

  As shown in FIG. 1, the tractor 10 includes a vehicle body 11, a pair of left and right front wheels (running unit) 12, and a pair of left and right rear wheels (running unit) 13. A bonnet 14 is disposed at the front of the vehicle body 11, and an engine 15 is disposed inside the bonnet 14.

  A mission case 16 is disposed between the pair of left and right rear wheels 13. The output of the engine 15 is shifted by a hydraulic-mechanical transmission (hereinafter referred to as “HMT”) 17 in the transmission case 16 and transmitted to the rear wheel 13. Details of the HMT 17 will be described later.

  A lower link 18, a top link 19, and a PTO shaft 20 are disposed at the rear of the mission case 16. A work machine lifting mechanism 21 is attached to the top of the mission case 16. The work machine is connected to the lower link 18 and the top link 19 and is driven by the PTO shaft 20. Moreover, the working machine lifting mechanism 21 can lift and lower the connected working machines.

  A cabin 22 for an operator (driver) to board is disposed above the mission case 16 and behind the hood 14. A driver seat 70 is provided inside the cabin 22, and a number of operating tools for operation by an operator are provided in the vicinity of the driver seat 70. The operator operates the operation tool to run the tractor 10 and operate various attachments. Details of this operation tool will be described later.

  Next, the configuration of the drive transmission path of this embodiment, particularly the HMT (continuously variable transmission) 17, will be described with reference to FIG. FIG. 2 is a skeleton diagram showing the power transmission path of the tractor 10. The HMT 17 includes an HST (hydrostatic continuously variable transmission) 30 and a planetary gear mechanism 40.

  The HST 30 includes a hydraulic pump 31 and a hydraulic motor 32. The hydraulic pump 31 discharges hydraulic oil when the output of the engine 15 is transmitted through the engine output shaft 15a. The hydraulic pump 31 includes a movable swash plate 31a, and the flow rate of discharged hydraulic oil changes according to the inclination angle of the movable swash plate 31a. The hydraulic motor 32 is driven by hydraulic oil discharged from the hydraulic pump 31. The output of the hydraulic motor 32 is transmitted to the planetary gear mechanism 40 via the motor output shaft 32a.

  With this configuration, the output of the engine 15 can be shifted and transmitted to the planetary gear mechanism 40 by controlling the inclination angle of the movable swash plate 31a.

  The planetary gear mechanism 40 includes a sun gear 41, an internal gear 42, a carrier 43, a planetary gear 44, and a plurality of gears and a transmission shaft.

  The output of the engine 15 is transmitted to the gear 45 via the engine output shaft 15a. The power transmitted to the gear 45 is transmitted to the planetary gear 44 via the gear 46 and the sun gear 41. On the other hand, the output of the HST 30 is transmitted to the planetary gear 44 via the motor output shaft 32a, the gear 47, and the internal gear 42 having teeth formed on the inner and outer circumferences.

  In this way, power is transmitted to the planetary gear 44 from two paths. The planetary gear 44 rotates around the planetary axis and revolves around the HMT output shaft 48. The power generated by the rotation of the planetary gear 44 is transmitted to the gear 49. The power generated by the revolution of the planetary gear 44 is transmitted to the carrier 43. The power transmitted to the gear 49 is used as power on the high speed side, and the power transmitted to the carrier 43 is used as power on the low speed side.

  The planetary gear mechanism 40 includes a high speed side clutch 51 and a low speed side clutch 52. The high-speed side clutch 51 can be switched between transmitting power from the gear 49 to the HMT output shaft 48 or shutting it off. The low speed side clutch 52 can be switched between transmitting power from the carrier 43 to the HMT output shaft 48 or shutting it off. Note that the output of the engine 15 is not transmitted to the rear wheel 13 side because both the high speed side clutch 51 and the low speed side clutch 52 cut off the power.

  Further, the power transmitted to the carrier 43 is transmitted to the reverse gear 55 via the gear 53 and the gear 54. When the reverse gear 55 and the HMT output shaft 48 are connected by the reverse clutch 56 in a state where both the high speed side clutch 51 and the low speed side clutch 52 are shut off, the power of the reverse gear 55 is transferred to the HMT output shaft 48. Communicated. Thereby, the HMT output shaft 48 can be rotated in the reverse direction.

  As described above, the output of the engine 15 and the output of the HST 30 are combined in the planetary gear mechanism 40, and the combined output is transmitted to the HMT output shaft 48.

  Further, an auxiliary transmission 60 and a differential mechanism 65 are arranged downstream of the planetary gear mechanism 40 in the power transmission direction. The auxiliary transmission 60 changes the power transmitted from the planetary gear mechanism 40. The auxiliary transmission 60 includes two gears 61 and 62 having different gear diameters, and an auxiliary transmission clutch 63. The sub-transmission clutch 63 performs a shift by switching between a state where power is transmitted by the gear 61 and a state where power is transmitted by the gear 62. The power changed in the auxiliary transmission 60 is transmitted to the differential mechanism 65 via the auxiliary transmission output shaft 64.

  The differential mechanism 65 distributes the power transmitted from the auxiliary transmission 60 to the left and right. The power distributed by the differential mechanism 65 is transmitted to the left and right rear wheels 13, respectively.

  Next, with reference to FIG.3 and FIG.4, the operation tool arrange | positioned inside the cabin 22 is demonstrated. FIG. 3 is a plan view showing an operation tool provided in the cabin 22. FIG. 4 is a block diagram showing a configuration for controlling the HMT 17.

  As shown in FIG. 3, a driver seat 70 is disposed inside the cabin 22. A shift lever (vehicle speed operation unit) 71 and a speed adjustment dial (vehicle speed operation unit) 72 are arranged on the right side of the driver seat 70. As shown in FIG. 4, the tractor 10 includes a shift lever sensor 71 a, a dial sensor 72 a, and a transmission control unit (control unit) 100 that controls the HMT 17.

  The transmission lever 71 is an operating tool for setting the set vehicle speed (maximum vehicle speed) of the tractor 10. The transmission lever 71 is configured to be slidable in the front-rear direction. The shift lever sensor 71 a detects the position of the shift lever 71 and outputs it to the transmission control unit 100. The transmission control unit 100 changes the inclination angle of the movable swash plate 31a based on the input content to perform a shift.

  The speed adjustment dial 72 is an operation tool for adjusting the set vehicle speed set by the speed change lever 71. The speed adjustment dial 72 of the present embodiment can be adjusted in two steps, low speed and high speed, but the vehicle speed may be adjusted steplessly. The dial sensor 72 a detects whether the setting of the speed adjustment dial 72 is low speed or high speed and outputs it to the transmission control unit 100. The transmission control unit 100 controls the auxiliary transmission clutch 63 based on the input content, and causes the vehicle body 11 to travel at the set vehicle speed.

  A clutch pedal 73 and a brake pedal 74 are disposed below the driver seat 70. In addition, the tractor 10 includes a potentiometer (depression amount detection unit) 73a, a clutch pedal switch 73b, and a brake pedal switch 74a.

  The clutch pedal 73 is an operating tool for switching between a transmission state in which the output of the engine 15 is transmitted to the rear wheel 13 side and a cutoff state in which the output is blocked. The potentiometer 73a detects the depression amount of the clutch pedal 73 and outputs it to the transmission control unit 100. The clutch pedal switch 73b detects whether or not the amount of depression of the clutch pedal 73 is greater than or equal to a threshold (specifically, a second threshold described later) and outputs the detected value to the transmission control unit 100. The transmission control unit 100 switches between the transmission state and the cutoff state by controlling the high speed side clutch 51 and the low speed side clutch 52 in accordance with the depression amount (rotation angle) of the clutch pedal 73. Further, the transmission control unit 100 according to the present embodiment controls the movable swash plate 31a, the high speed side clutch 51, the low speed side clutch 52, and the like according to the depression amount of the clutch pedal 73, and adjusts the vehicle speed. At this time, the engine speed may be adjusted. How to adjust the vehicle speed according to the depression amount of the clutch pedal 73 will be described later.

  The brake pedal 74 includes a left brake pedal and a right brake pedal, and can perform braking by operating brakes disposed on the left rear wheel and the right rear wheel, respectively. When it is not necessary to brake the left and right rear wheels separately, the left brake pedal and the right brake pedal are connected by a connection plate (not shown). The brake pedal switch 74a detects whether or not the amount of depression of the brake pedal 74 is greater than or equal to a predetermined value, and outputs it to the transmission control unit 100. When the depression amount of the brake pedal 74 is greater than or equal to a predetermined amount, the transmission control unit 100 controls the movable swash plate 31a with the target value of the movable swash plate 31a as a neutral position (an angle corresponding to a vehicle speed of zero). Do. The angle of the movable swash plate 31a may be detected by a sensor, or may be estimated from the ratio between the vehicle speed and the engine speed.

  In front of the driver's seat 70, a steering wheel 75 for an operator to switch the traveling direction of the tractor 10 is disposed. In the vicinity of the steering 75, a reverser lever 76 and a work implement lifting lever 77 are disposed. The tractor 10 includes a reverser lever switch 76a.

  The reverser lever 76 is an operating tool for switching between forward and backward movement of the tractor 10. The reverser lever switch 76a detects whether the position of the reverser lever 76 is the forward position or the reverse position, and outputs the detected position to the transmission control unit 100. The transmission control unit 100 switches the forward and backward movements of the tractor 10 by switching the reverse clutch 56 based on the input content.

  The work implement lifting lever 77 is an operation tool for raising and lowering the work implement. When the operator operates the work implement lifting lever 77, the operation is detected by a sensor (not shown). The work implement can be moved up and down by operating the work implement lifting mechanism 21 in accordance with the detection result output by the sensor.

  In addition, the vehicle speed is input from the vehicle speed sensor 78 and the engine speed (engine speed) is input from the engine speed sensor 79 to the transmission control unit 100.

  Next, with reference to FIGS. 5 to 7, control for adjusting the vehicle speed based on the amount of depression of the clutch pedal 73 (hereinafter referred to as the amount of depression) (hereinafter referred to as vehicle speed adjustment control) will be described. FIG. 5 is a flowchart illustrating vehicle speed adjustment control performed by the transmission control unit 100.

  When the transmission control unit 100 acquires the depression amount from the potentiometer 73a (S101), the transmission control unit 100 determines whether or not the depression amount is equal to or greater than the first threshold (S102). The first threshold value is a threshold value that determines whether or not to perform the current control (in other words, a value that determines the play portion of the clutch pedal 73). Therefore, the first threshold value is preferably a value with a relatively small amount of depression. If the transmission control unit 100 determines that the amount of depression is smaller than the first threshold, for example, the process of S101 is performed again after a predetermined time.

  When determining that the stepping amount is equal to or greater than the first threshold, the transmission control unit 100 determines whether the stepping amount is equal to or larger than the second threshold (S103). Since this threshold value is a value for switching between the clutch transmission state and the disengagement state, it is preferable that the depression amount is a relatively large value (a little before the depression amount limit value).

  The transmission control unit 100 performs vehicle speed adjustment control when the depression amount is smaller than the second threshold value. First, the transmission control unit 100 calculates the pedal adjustment vehicle speed based on the depression amount (S104). The pedal adjustment vehicle speed is a vehicle speed calculated according to the depression amount. The transmission control unit 100 stores the correspondence (the contents of the graph shown in FIG. 6) between the depression amount and the pedal adjustment vehicle speed. This correspondence is set in advance, but the value can be changed by the setting of the manufacturer or operator of the tractor 10.

  Since the vehicle speed adjustment control is performed when the depression amount is between the first threshold value and the second threshold value, the pedal adjustment vehicle speed is set for the depression amount in this range. As shown in the graph of FIG. 6, the pedal adjustment vehicle speed is set to decrease as the depression amount increases. In this embodiment, the depression amount and the pedal adjustment vehicle speed are in a proportional relationship (inclination is constant), but the correspondence may be determined so that the inclination changes. Further, this correspondence relationship may be changed stepwise (stepwise) without being continuously changed. The transmission control unit 100 calculates and stores the pedal adjustment vehicle speed corresponding to the detected depression amount.

  Next, the transmission control unit 100 determines whether or not the pedal adjustment vehicle speed is smaller than the set vehicle speed set by the transmission lever 71 or the like (S105). If the pedal adjustment vehicle speed is smaller than the set vehicle speed, the transmission control unit 100 controls the HMT 17 using the pedal adjustment vehicle speed as the target vehicle speed (S106). Further, when the pedal adjustment vehicle speed is equal to or higher than the set vehicle speed, the transmission control unit 100 controls the HMT 17 using the pedal adjustment vehicle speed as the target vehicle speed (S107). Since the current vehicle speed is input from the vehicle speed sensor 78 to the transmission control unit 100, the current vehicle speed is brought close to the target vehicle speed by feedback control, for example. In addition, it is preferable that the target vehicle speed determined here is 10 km / h or less, or 5 km / h or less, for example.

  Thereby, it can prevent reliably exceeding the setting vehicle speed which the operator set. For this reason, it is possible to prevent the vehicle speed from becoming higher than the operator's assumption and failing to work or feeling uncomfortable.

  After that, the transmission control unit 100 again performs the processes after S101 to update the target vehicle speed and adjust the vehicle speed. As described above, even when the HMT 17 is provided, the operation feeling similar to that of the half clutch can be realized by using the clutch pedal 73.

  If the transmission control unit 100 determines in step S103 that the depression amount is greater than the second threshold, the transmission control unit 100 determines whether the switch of the clutch pedal switch 73b is ON or OFF (S108). As described above, the clutch pedal switch 73b is turned on when the depression amount is larger than the second threshold value. Accordingly, the clutch pedal switch should normally be turned on. In this case, the transmission control unit 100 controls the high speed side clutch 51 and the low speed side clutch 52 to switch to the disconnected state (turns the clutch off, S109).

  On the other hand, when the clutch pedal switch 73b is OFF, it is determined that at least one of the potentiometer 73a and the clutch pedal switch 73b is abnormal (S110). In this case, the tractor 10 may notify the user to that effect and shift to the fail safe mode. Further, when the sensor having the abnormality can be specified by other means, the clutch may be controlled based only on the sensor having no abnormality.

  As described above, the abnormality of any one of the sensors can be determined by providing a plurality of sensors for detecting the depression amount. Note that the clutch pedal switch 73b may be omitted, or two or more clutch pedal switches 73b may be provided. When two or more clutch pedal switches 73b are provided, for example, the first threshold value and the second threshold value can be detected.

  Next, a change in the vehicle speed when the amount of depression of the clutch pedal 73 is changed will be described with reference to FIG. FIG. 7 is a diagram illustrating how the vehicle speed changes in accordance with the amount of depression of the clutch pedal. In FIG. 7, the vertical axis represents vehicle speed and the horizontal axis represents time. In addition, on the horizontal axis, time zones A to F are described, and below that, the amount of depression in each time zone is described.

  In time zone A, the amount of depression is less than the first threshold value, so vehicle speed adjustment control is not performed. For this reason, the set vehicle speed set by the speed change lever 71 and the speed adjustment dial 72 matches the actual vehicle speed. Thereafter, when the operator depresses the clutch pedal 73, vehicle speed adjustment control is performed, and processing for reducing the vehicle speed is performed. In time zone B, the amount of depression is small, so the vehicle speed is fast, and in time zone C, the amount of depression is large, so the vehicle speed is slow. In the time zone D, the clutch pedal 73 is further depressed and the depression amount is equal to or greater than the second threshold value, so that the disengaged state (clutch is OFF).

  Thereafter, when the clutch pedal 73 is released a little, the depression amount becomes smaller than the second threshold value, and the transmission state (clutch is ON) is established. In time zone E, the amount of depression is between time zone B and time zone C, so the vehicle speed is also between time zone B and time zone C. In the time zone F, the clutch pedal 73 is released and the depression amount becomes less than the first threshold value, and the vehicle speed adjustment control is not performed (runs at the set vehicle speed). In this manner, the operator can finely adjust the vehicle speed like a half clutch by adjusting the depression amount of the clutch pedal 73.

  Next, a modification of the first embodiment will be described. In the first embodiment, when the pedal adjustment vehicle speed is smaller than the set vehicle speed, the target vehicle speed is determined based only on the depression amount, but the target vehicle speed may be calculated in consideration of other values. Examples of the value to be considered include a set vehicle speed or an engine speed.

  When considering the set vehicle speed, for example, a correction ratio (a predetermined value from 0 to 1) is calculated based on the depression amount. This correction ratio decreases as the depression amount increases. The transmission control unit 100 sets a value obtained by multiplying the set vehicle speed by the correction ratio as the target vehicle speed. Thereby, the structure which becomes low in vehicle speed according to the depression amount is realizable.

  Further, for example, the target vehicle speed may be calculated by calculating a correction coefficient based on the set vehicle speed and adding the pedal adjustment vehicle speed obtained in the above embodiment to the correction coefficient.

  When considering the engine speed, for example, a correction coefficient is calculated based on the engine speed, and the target vehicle speed can be calculated by adding the pedal adjustment vehicle speed obtained in the above embodiment to this correction coefficient. it can. The method using the set vehicle speed and the engine speed is arbitrary, and can be changed as appropriate.

  In the above description, the vehicle speed is controlled based on the depression amount of the clutch pedal 73. However, similar control can be performed on the brake pedal 74 based on the depression amount. In this case, a depression amount detection unit such as a potentiometer is disposed on the brake pedal 74. When the brake pedal 74 is depressed more than a predetermined threshold value, the tractor 10 can be stopped using a mechanical braking device such as a drum brake while cutting off the power transmitted from the engine 15 to the rear wheel 13. it can. The transmission control unit 100 controls the vehicle speed based on the depression amount of the brake pedal 74 in the same manner as described above. The vehicle speed may be controlled based on the depression amount of only one of the clutch pedal 73 and the brake pedal 74, or the vehicle speed may be controlled based on the depression amounts of both the clutch pedal 73 and the brake pedal 74. good.

  Next, a second embodiment will be described with reference to FIG. In the description of the second embodiment, components that are the same as or similar to those in the above embodiment may be given the same reference numerals in the drawings to simplify the description.

  The transmission 82 according to the second embodiment is a hydraulic-mechanical continuously variable transmission that performs a shift without using a planetary gear mechanism. The transmission 82 may be a hydrostatic continuously variable transmission (HST). The transmission 82 is an inline transmission that includes an input shaft 81 to which power of the engine 15 is input and a cylindrical output shaft 83 that is disposed outside the input shaft.

  The output of the output shaft 83 is transmitted to the forward clutch 86 via the gear 84 and the forward rotation gear 85. The output of the output shaft 83 is transmitted to the reverse clutch 89 via the gear 84, the counter shaft 87 and the reverse gear 88. By controlling the forward clutch 86 and the reverse clutch 89, the rotation direction of the transmission shaft 90 can be switched.

  The sub-transmission device 60 includes gears 61 and 62 having different diameters as in the present embodiment, and transmits the power of the transmission shaft 90 to the sub-transmission shaft 92 via any one of the gears. The power transmitted to the auxiliary transmission shaft 92 is transmitted to the rear wheel 13 via the differential mechanism 65 and also to the front wheel 12 via a differential mechanism for front wheels (not shown).

  As described above, the tractor 10 according to the present embodiment includes the engine 15, the hydraulic HMT 17, the front wheels 12 and the rear wheels 13, the potentiometer 73a, and the transmission control unit 100. The hydraulic HMT 17 changes the output of the engine 15. The front wheel 12 and the rear wheel 13 cause the vehicle body 11 to travel using the output of the HMT 17. The potentiometer 73a detects the depression amount of the clutch pedal 73. The transmission control unit 100 calculates the target vehicle speed based on the depression amount detected by the potentiometer 73a, and performs control to change the vehicle speed based on the target vehicle speed.

  Thereby, since the clutch pedal 73 can be operated with a foot, the speed of the tractor 10 can be adjusted even in a situation where it is difficult to operate the speed change lever 71 or the speed adjustment dial 72. Therefore, the speed of the tractor 10 can be finely adjusted by a simple operation even when the work implement is attached or detached or when the work is performed on the heel.

  Further, in the tractor 10 of the present embodiment, the potentiometer 73a detects the depression amount of the clutch pedal. The transmission control unit 100 cuts off the power transmitted from the engine 15 to the front wheels 12 or the rear wheels 13 when the amount of depression exceeds a predetermined threshold value.

  Thus, since the vehicle speed is controlled based on the depression amount of the clutch pedal, the operator can finely adjust the vehicle speed with the same operation feeling as that of the half clutch.

  In the tractor 10 of the present embodiment, a vehicle speed corresponding to the depression amount is set in advance. The transmission control unit 100 controls the vehicle speed corresponding to the depression amount detected by the depression potentiometer 73a as the target vehicle speed.

  As a result, the vehicle speed is determined only in accordance with the depression amount, so that the operator can easily realize the desired vehicle speed by learning the correspondence between the depression amount and the vehicle speed.

  Although the embodiment and the modification of the present invention have been described above, the above configuration can be modified as follows, for example.

  In the HMT 17 of the first embodiment, the output of the engine 15 and the output of the HST 30 are combined in the planetary gear mechanism 40, and the combined output is transmitted to the HMT output shaft 48. In this regard, the HMT 17 may be configured to be able to switch between transmitting the synthesized output to the HMT output shaft or outputting the HST output directly to the HMT output shaft.

  In the above, only the hydraulic pump 31 is a variable displacement type, but the hydraulic motor 32 may be a variable displacement type, and both the hydraulic pump 31 and the hydraulic motor 32 may be a variable displacement type.

  In the above description, the depression amount of the clutch pedal 73 or the brake pedal 74 is detected by the potentiometer 73a, but the depression amount may be detected by another sensor (such as a pressure sensor).

  In the above description, the set vehicle speed is set by two operation units, but the configuration may be such that the set vehicle speed is set by one operation unit.

  The transmission control unit 100 may be provided inside an ECU (engine control unit), or may be provided separately from the ECU.

  The present invention is not limited to a four-wheel tractor, and can be applied to, for example, a semi-crawler tractor. It can also be applied to work vehicles other than tractors (rice transplanters, etc.).

10 Tractor (work vehicle)
11 body 12 front wheel (traveling part)
13 Rear wheel (travel section)
15 engine 17 HMT (continuously variable transmission)
30 HST
40 Planetary gear mechanism 71 Shift lever (vehicle speed control unit)
72 Speed adjustment dial (vehicle speed control section)
73 Clutch pedal 73a Potentiometer (depression amount detector)
74 Brake pedal 100 Transmission control unit (control unit)

Claims (4)

  1. Engine,
    A hydraulic continuously variable transmission for shifting the output of the engine;
    A traveling unit that causes the vehicle body to travel by the output of the continuously variable transmission,
    A depression amount detector for detecting the depression amount of the clutch pedal or the brake pedal;
    A control unit that calculates a target vehicle speed that decreases as the stepping amount increases based on the stepping amount detected by the stepping amount detection unit, and performs control to change the vehicle speed based on the target vehicle speed;
    A work vehicle comprising:
  2. The work vehicle according to claim 1,
    The depression amount detection unit detects the depression amount of the clutch pedal or the brake pedal,
    The control unit cuts off power transmitted from the engine to the traveling unit when the amount of depression becomes a predetermined threshold or more.
  3. The work vehicle according to claim 1 or 2,
    A vehicle speed corresponding to the amount of depression is preset,
    The control unit controls the vehicle speed corresponding to the stepping amount detected by the stepping amount detection unit as the target vehicle speed.
  4. The work vehicle according to claim 1 or 2,
    It has a vehicle speed control unit that can control the vehicle speed,
    The control unit determines a vehicle speed based on at least one of an instruction content of the vehicle speed operation unit and an engine rotation speed in addition to the depression amount detected by the depression amount detection unit, and determines the determined vehicle speed as the target A work vehicle that is controlled as a vehicle speed.
JP2014124080A 2014-06-17 2014-06-17 Work vehicle Pending JP2016003707A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2014124080A JP2016003707A (en) 2014-06-17 2014-06-17 Work vehicle

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2014124080A JP2016003707A (en) 2014-06-17 2014-06-17 Work vehicle

Publications (1)

Publication Number Publication Date
JP2016003707A true JP2016003707A (en) 2016-01-12

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Family Applications (1)

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JP2014124080A Pending JP2016003707A (en) 2014-06-17 2014-06-17 Work vehicle

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JP (1) JP2016003707A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002274353A (en) * 2001-03-16 2002-09-25 Nissan Motor Co Ltd Vehicular braking/driving force control device
JP2008223815A (en) * 2007-03-09 2008-09-25 Kayaba Ind Co Ltd Automotive control device for mechanical throttle vehicle

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002274353A (en) * 2001-03-16 2002-09-25 Nissan Motor Co Ltd Vehicular braking/driving force control device
JP2008223815A (en) * 2007-03-09 2008-09-25 Kayaba Ind Co Ltd Automotive control device for mechanical throttle vehicle

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